A hyroformylation reaction that is generally well known as OXO reaction is a process for producing linear (normal) and branched (iso) aldehyde, in which the olefin is added with one carbon number by reacting all kinds of olefins and synthesis gas (CO/H2) under presence of metal catalyst and ligand.
All kinds of aldehydes that are synthesized by OXO reaction are modified into alcohol and acid that are aldehyde derivatives through an oxidation or reduction reaction. Also, they can be modified into various acids and alcohols comprising long alkyl group through an oxidation or reduction reaction after a condensation reaction, such as aldol, and the like. Those alcohols and acids are being used as a raw material for solvent, additive and all kinds of plasticizers.
The representative example of the hydroformylation is to produce octanol (2-ethylhexanol) from propylene using a rhodium-based catalyst. Octanol is mainly used as a raw material for PVC plasticizer, such as dioctyl phthalate (DOP), and also as an intermediate raw material for synthesis lubricant, surfactant, and the like.
Propylene is injected with a catalyst into OXO reactor using a catalyst to produce normal-butylaldehydes and iso-butylaldehydes. The produced aldehydes mixture is transferred to a separator along with catalyst mixture to separate into hydrocarbon and catalyst mixture, and then the catalyst mixture is circulated into the reactor and the hydrocarbon is transferred to a stripper. The hydrocarbon in the stripper is stripped by fresh synthesis gas to recover non-reacted propylene and synthesis gas into OXO reactor and transfer butylaldehydes to a fractionation column thereby separating normal- and iso-butylaldehydes, respectively. Normal-butylaldehydes of the fractionation column bottom is transferred to a hydrotreated reactor, and then adding hydrogen produces n-butanol. Alternatively, normal-butylaldehydes is introduced into an aldol condensation reactor to produce 2-ethylhexanal through a condensation and dehydration reaction, and then is transferred to the hydrotreated reactor to be octanol (2-ethylhexanol) by adding hydrogen.
The hydroformylation reaction may be preformed in a continuous way, semi-continuous way or batch way, and the typical hydroformylation reaction is a gas or liquid recirculation system. It is important for the hydroformylation reaction to increase the reaction efficiency by smoothly contacting the starting materials that are composed of a liquid phase and gas phase. For this reason, conventionally the continuous stirred tank reactor (CSTR) that stirs for evenly contacting the components of liquid phase and gas phase inside the reactor was mainly used. In addition, U.S. Pat. No. 5,763,678 discloses the hydroformylation method, in which the circulation is used instead of the stirring by applying the reactor that is a type of loop. However, those methods have a limit to the improvement of the hydroformylation reaction efficiency and also single reactor cannot produce the satisfactory aldehyde product, so that the residence time of the reaction is made to be longer, or more than two reactors are connected in series thereby producing the product that has a required level.
In addition, the hydrogenation process of aldehydes generally uses the reactor, in which nickel-based or copper-based solid hydrogenation catalyst is filled inside the reactor. There are two ways for performing the reaction, such that the starting aldehydes are evaporated to perform the reaction in a vapor phase, or the starting aldehyes are introduced into the reactor as a liquid to perform the reaction in a liquid phase.
However, there is a problem that the selectivity of the reaction is reduced by generating an undesirable side reaction, such as esterification, acetal formation, etherification, and the like in the above reaction, even though the above catalysts types, the vapor phase, or the liquid phase are applied.